[PATCH v9 5/8] KVM: Register/unregister the guest private memory regions

Chao Peng
2022-10-25T15:20:42Z

Introduce generic private memory register/unregister by reusing existing
SEV ioctls KVM_MEMORY_ENCRYPT_{UN,}REG_REGION. It differs from SEV case
by treating address in the region as gpa instead of hva. Which cases
should these ioctls go is determined by the kvm_arch_has_private_mem().
Architecture which supports KVM_PRIVATE_MEM should override this function.

KVM internally defaults all guest memory as private memory and maintain
the shared memory in 'mem_attr_array'. The above ioctls operate on this
field and unmap existing mappings if any.

Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
---
Documentation/virt/kvm/api.rst | 17 ++-
arch/x86/kvm/Kconfig | 1 +
include/linux/kvm_host.h | 10 +-
virt/kvm/Kconfig | 4 +
virt/kvm/kvm_main.c | 227 +++++++++++++++++++++++++--------
5 files changed, 198 insertions(+), 61 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 975688912b8c..08253cf498d1 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -4717,10 +4717,19 @@ Documentation/virt/kvm/x86/amd-memory-encryption.rst.
This ioctl can be used to register a guest memory region which may
contain encrypted data (e.g. guest RAM, SMRAM etc).

-It is used in the SEV-enabled guest. When encryption is enabled, a guest
-memory region may contain encrypted data. The SEV memory encryption
-engine uses a tweak such that two identical plaintext pages, each at
-different locations will have differing ciphertexts. So swapping or
+Currently this ioctl supports registering memory regions for two usages:
+private memory and SEV-encrypted memory.
+
+When private memory is enabled, this ioctl is used to register guest private
+memory region and the addr/size of kvm_enc_region represents guest physical
+address (GPA). In this usage, this ioctl zaps the existing guest memory
+mappings in KVM that fallen into the region.
+
+When SEV-encrypted memory is enabled, this ioctl is used to register guest
+memory region which may contain encrypted data for a SEV-enabled guest. The
+addr/size of kvm_enc_region represents userspace address (HVA). The SEV
+memory encryption engine uses a tweak such that two identical plaintext pages,
+each at different locations will have differing ciphertexts. So swapping or
moving ciphertext of those pages will not result in plaintext being
swapped. So relocating (or migrating) physical backing pages for the SEV
guest will require some additional steps.
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 8d2bd455c0cd..73fdfa429b20 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -51,6 +51,7 @@ config KVM
select HAVE_KVM_PM_NOTIFIER if PM
select HAVE_KVM_RESTRICTED_MEM if X86_64
select RESTRICTEDMEM if HAVE_KVM_RESTRICTED_MEM
+ select KVM_GENERIC_PRIVATE_MEM if HAVE_KVM_RESTRICTED_MEM
help
Support hosting fully virtualized guest machines using hardware
virtualization extensions. You will need a fairly recent
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 79e5cbc35fcf..4ce98fa0153c 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -245,7 +245,8 @@ bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
#endif

-#ifdef KVM_ARCH_WANT_MMU_NOTIFIER
+
+#if defined(KVM_ARCH_WANT_MMU_NOTIFIER) || defined(CONFIG_KVM_GENERIC_PRIVATE_MEM)
struct kvm_gfn_range {
struct kvm_memory_slot *slot;
gfn_t start;
@@ -254,6 +255,9 @@ struct kvm_gfn_range {
bool may_block;
};
bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range);
+#endif
+
+#ifdef KVM_ARCH_WANT_MMU_NOTIFIER
bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
@@ -794,6 +798,9 @@ struct kvm {
struct notifier_block pm_notifier;
#endif
char stats_id[KVM_STATS_NAME_SIZE];
+#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
+ struct xarray mem_attr_array;
+#endif
};

#define kvm_err(fmt, ...) \
@@ -1453,6 +1460,7 @@ bool kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu);
int kvm_arch_post_init_vm(struct kvm *kvm);
void kvm_arch_pre_destroy_vm(struct kvm *kvm);
int kvm_arch_create_vm_debugfs(struct kvm *kvm);
+bool kvm_arch_has_private_mem(struct kvm *kvm);

#ifndef __KVM_HAVE_ARCH_VM_ALLOC
/*
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 9ff164c7e0cc..69ca59e82149 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -89,3 +89,7 @@ config HAVE_KVM_PM_NOTIFIER

config HAVE_KVM_RESTRICTED_MEM
bool
+
+config KVM_GENERIC_PRIVATE_MEM
+ bool
+ depends on HAVE_KVM_RESTRICTED_MEM
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 09c9cdeb773c..fc3835826ace 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -520,6 +520,62 @@ void kvm_destroy_vcpus(struct kvm *kvm)
}
EXPORT_SYMBOL_GPL(kvm_destroy_vcpus);

+static inline void update_invalidate_range(struct kvm *kvm, gfn_t start,
+ gfn_t end)
+{
+ if (likely(kvm->mmu_invalidate_in_progress == 1)) {
+ kvm->mmu_invalidate_range_start = start;
+ kvm->mmu_invalidate_range_end = end;
+ } else {
+ /*
+ * Fully tracking multiple concurrent ranges has diminishing
+ * returns. Keep things simple and just find the minimal range
+ * which includes the current and new ranges. As there won't be
+ * enough information to subtract a range after its invalidate
+ * completes, any ranges invalidated concurrently will
+ * accumulate and persist until all outstanding invalidates
+ * complete.
+ */
+ kvm->mmu_invalidate_range_start =
+ min(kvm->mmu_invalidate_range_start, start);
+ kvm->mmu_invalidate_range_end =
+ max(kvm->mmu_invalidate_range_end, end);
+ }
+}
+
+static void mark_invalidate_in_progress(struct kvm *kvm, gfn_t start, gfn_t end)
+{
+ /*
+ * The count increase must become visible at unlock time as no
+ * spte can be established without taking the mmu_lock and
+ * count is also read inside the mmu_lock critical section.
+ */
+ kvm->mmu_invalidate_in_progress++;
+}
+
+void kvm_mmu_invalidate_begin(struct kvm *kvm, gfn_t start, gfn_t end)
+{
+ mark_invalidate_in_progress(kvm, start, end);
+ update_invalidate_range(kvm, start, end);
+}
+
+void kvm_mmu_invalidate_end(struct kvm *kvm, gfn_t start, gfn_t end)
+{
+ /*
+ * This sequence increase will notify the kvm page fault that
+ * the page that is going to be mapped in the spte could have
+ * been freed.
+ */
+ kvm->mmu_invalidate_seq++;
+ smp_wmb();
+ /*
+ * The above sequence increase must be visible before the
+ * below count decrease, which is ensured by the smp_wmb above
+ * in conjunction with the smp_rmb in mmu_invalidate_retry().
+ */
+ kvm->mmu_invalidate_in_progress--;
+}
+
#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
static inline struct kvm *mmu_notifier_to_kvm(struct mmu_notifier *mn)
{
@@ -715,51 +771,12 @@ static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn,
kvm_handle_hva_range(mn, address, address + 1, pte, kvm_set_spte_gfn);
}

-static inline void update_invalidate_range(struct kvm *kvm, gfn_t start,
- gfn_t end)
-{
- if (likely(kvm->mmu_invalidate_in_progress == 1)) {
- kvm->mmu_invalidate_range_start = start;
- kvm->mmu_invalidate_range_end = end;
- } else {
- /*
- * Fully tracking multiple concurrent ranges has diminishing
- * returns. Keep things simple and just find the minimal range
- * which includes the current and new ranges. As there won't be
- * enough information to subtract a range after its invalidate
- * completes, any ranges invalidated concurrently will
- * accumulate and persist until all outstanding invalidates
- * complete.
- */
- kvm->mmu_invalidate_range_start =
- min(kvm->mmu_invalidate_range_start, start);
- kvm->mmu_invalidate_range_end =
- max(kvm->mmu_invalidate_range_end, end);
- }
-}
-
-static void mark_invalidate_in_progress(struct kvm *kvm, gfn_t start, gfn_t end)
-{
- /*
- * The count increase must become visible at unlock time as no
- * spte can be established without taking the mmu_lock and
- * count is also read inside the mmu_lock critical section.
- */
- kvm->mmu_invalidate_in_progress++;
-}
-
static bool kvm_mmu_handle_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
{
update_invalidate_range(kvm, range->start, range->end);
return kvm_unmap_gfn_range(kvm, range);
}

-void kvm_mmu_invalidate_begin(struct kvm *kvm, gfn_t start, gfn_t end)
-{
- mark_invalidate_in_progress(kvm, start, end);
- update_invalidate_range(kvm, start, end);
-}
-
static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
const struct mmu_notifier_range *range)
{
@@ -807,23 +824,6 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
return 0;
}

-void kvm_mmu_invalidate_end(struct kvm *kvm, gfn_t start, gfn_t end)
-{
- /*
- * This sequence increase will notify the kvm page fault that
- * the page that is going to be mapped in the spte could have
- * been freed.
- */
- kvm->mmu_invalidate_seq++;
- smp_wmb();
- /*
- * The above sequence increase must be visible before the
- * below count decrease, which is ensured by the smp_wmb above
- * in conjunction with the smp_rmb in mmu_invalidate_retry().
- */
- kvm->mmu_invalidate_in_progress--;
-}
-
static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
const struct mmu_notifier_range *range)
{
@@ -937,6 +937,89 @@ static int kvm_init_mmu_notifier(struct kvm *kvm)

#endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */

+#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
+
+static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end)
+{
+ struct kvm_gfn_range gfn_range;
+ struct kvm_memory_slot *slot;
+ struct kvm_memslots *slots;
+ struct kvm_memslot_iter iter;
+ int i;
+ int r = 0;
+
+ gfn_range.pte = __pte(0);
+ gfn_range.may_block = true;
+
+ for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
+ slots = __kvm_memslots(kvm, i);
+
+ kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) {
+ slot = iter.slot;
+ gfn_range.start = max(start, slot->base_gfn);
+ gfn_range.end = min(end, slot->base_gfn + slot->npages);
+ if (gfn_range.start >= gfn_range.end)
+ continue;
+ gfn_range.slot = slot;
+
+ r |= kvm_unmap_gfn_range(kvm, &gfn_range);
+ }
+ }
+
+ if (r)
+ kvm_flush_remote_tlbs(kvm);
+}
+
+#define KVM_MEM_ATTR_SHARED 0x0001
+static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size,
+ bool is_private)
+{
+ gfn_t start, end;
+ unsigned long i;
+ void *entry;
+ int idx;
+ int r = 0;
+
+ if (size == 0 || gpa + size < gpa)
+ return -EINVAL;
+ if (gpa & (PAGE_SIZE - 1) || size & (PAGE_SIZE - 1))
+ return -EINVAL;
+
+ start = gpa >> PAGE_SHIFT;
+ end = (gpa + size - 1 + PAGE_SIZE) >> PAGE_SHIFT;
+
+ /*
+ * Guest memory defaults to private, kvm->mem_attr_array only stores
+ * shared memory.
+ */
+ entry = is_private ? NULL : xa_mk_value(KVM_MEM_ATTR_SHARED);
+
+ idx = srcu_read_lock(&kvm->srcu);
+ KVM_MMU_LOCK(kvm);
+ kvm_mmu_invalidate_begin(kvm, start, end);
+
+ for (i = start; i < end; i++) {
+ r = xa_err(xa_store(&kvm->mem_attr_array, i, entry,
+ GFP_KERNEL_ACCOUNT));
+ if (r)
+ goto err;
+ }
+
+ kvm_unmap_mem_range(kvm, start, end);
+
+ goto ret;
+err:
+ for (; i > start; i--)
+ xa_erase(&kvm->mem_attr_array, i);
+ret:
+ kvm_mmu_invalidate_end(kvm, start, end);
+ KVM_MMU_UNLOCK(kvm);
+ srcu_read_unlock(&kvm->srcu, idx);
+
+ return r;
+}
+#endif /* CONFIG_KVM_GENERIC_PRIVATE_MEM */
+
#ifdef CONFIG_HAVE_KVM_PM_NOTIFIER
static int kvm_pm_notifier_call(struct notifier_block *bl,
unsigned long state,
@@ -1165,6 +1248,9 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
spin_lock_init(&kvm->mn_invalidate_lock);
rcuwait_init(&kvm->mn_memslots_update_rcuwait);
xa_init(&kvm->vcpu_array);
+#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
+ xa_init(&kvm->mem_attr_array);
+#endif

INIT_LIST_HEAD(&kvm->gpc_list);
spin_lock_init(&kvm->gpc_lock);
@@ -1338,6 +1424,9 @@ static void kvm_destroy_vm(struct kvm *kvm)
kvm_free_memslots(kvm, &kvm->__memslots[i][0]);
kvm_free_memslots(kvm, &kvm->__memslots[i][1]);
}
+#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
+ xa_destroy(&kvm->mem_attr_array);
+#endif
cleanup_srcu_struct(&kvm->irq_srcu);
cleanup_srcu_struct(&kvm->srcu);
kvm_arch_free_vm(kvm);
@@ -1541,6 +1630,11 @@ static void kvm_replace_memslot(struct kvm *kvm,
}
}

+bool __weak kvm_arch_has_private_mem(struct kvm *kvm)
+{
+ return false;
+}
+
static int check_memory_region_flags(const struct kvm_user_mem_region *mem)
{
u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
@@ -4708,6 +4802,24 @@ static long kvm_vm_ioctl(struct file *filp,
r = kvm_vm_ioctl_set_memory_region(kvm, &mem);
break;
}
+#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
+ case KVM_MEMORY_ENCRYPT_REG_REGION:
+ case KVM_MEMORY_ENCRYPT_UNREG_REGION: {
+ struct kvm_enc_region region;
+ bool set = ioctl == KVM_MEMORY_ENCRYPT_REG_REGION;
+
+ if (!kvm_arch_has_private_mem(kvm))
+ goto arch_vm_ioctl;
+
+ r = -EFAULT;
+ if (copy_from_user(&region, argp, sizeof(region)))
+ goto out;
+
+ r = kvm_vm_ioctl_set_mem_attr(kvm, region.addr,
+ region.size, set);
+ break;
+ }
+#endif
case KVM_GET_DIRTY_LOG: {
struct kvm_dirty_log log;

@@ -4861,6 +4973,9 @@ static long kvm_vm_ioctl(struct file *filp,
r = kvm_vm_ioctl_get_stats_fd(kvm);
break;
default:
+#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
+arch_vm_ioctl:
+#endif
r = kvm_arch_vm_ioctl(filp, ioctl, arg);
}
out:
--
2.25.1